1. Field of the Invention
The present invention relates to a process for preparing concentrated titanium minerals. More particularly, the invention relates to an improved process for preparing concentrated titanium minerals by leaching with an acid leaching agent to separate the iron components.
2. Description of the Prior Art
Titanium minerals are useful as raw materials for titanium dioxide. Thus, the preferable raw materials are the concentrated titanium minerals having high titanium content (for example, containing more than 90% by weight of TiO.sub.2) prepared by removing the iron components which are present in large amounts in the titanium minerals.
Oxidative thermal decomposition of tetrachlorotitanium, prepared by chlorinating a concentrated titanium mineral in a fluidized bed, has been effectively used for the preparation of titanium dioxide from the concentrated titanium mineral. In this method, if fine particles are contained in the concentrated titanium mineral fed at the chlorination stage, the fine particles will be carried along unreacted or incompletely reacted with the flow gas discharged from the reactor, resulting in loss of material, and transport difficulties, such as pipe clogging. Accordingly, fine particles are preferably omitted from the concentrated titanium mineral.
It is known that titanium minerals may be reduced and leached with acids, such as hydrochloric acid, to separate the iron components and thus prepare concentrated titanium minerals. However, by conventional processes, it is difficult to prevent the formation of large amounts of fine particles, especially particles having diameters of less than 10.mu.. Therefore, this method is clearly undesirable.
In the prior art concentrating procedure, the formation of a hard scale by deposition of a precipitate containing mainly TiO.sub.2 on the inner surface of the pipe connected to the leaching apparatus has been a serious problem during long term operation.
A need exists therefore for a method of concentrating titanium minerals by leaching, which will eliminate the formation of fine particles and inhibit scaling on the surfaces of the apparatus.